docs: def addToDefinition(self, json_dict):
          """
             The addToDefinition operation supports adding a definition
             property to a hosted feature service. The result of this
             operation is a response indicating success or failure with error
             code and description.
  
             This function will allow users to change add additional values
             to an already published service.
  
             Input:
                json_dict - part to add to host service.  The part format can
                            be derived from the asDictionary property.  For
                            layer level modifications, run updates on each
                            individual feature service layer object.
             Output:
                JSON message as dictionary
          """
          params = {
              "f" : "json",
              "addToDefinition" : json.dumps(json_dict),
              "async" : False
          }
          uURL = self._url + "/addToDefinition"
          res = self._post(url=uURL, param_dict=params,
                               securityHandler=self._securityHandler,
                               proxy_port=self._proxy_port,
                               proxy_url=self._proxy_url)
          self.refresh()
          return res